The present invention pertains to the integration of cylinders of a rotary printing machine into individual cylinder groups.
Prior-art rotary printing machines are driven by a main drive via a mechanical longitudinal shaft, also called a vertical shaft. One disadvantage of these printing machines is the mechanical effort that needs to be taken to compensate the torsion of the longitudinal shaft occurring during operation. As a result, it is necessary to mechanically adjust the circumferential register of print positions of the printing machine during operation.
Attempts have also been made to replace the mechanical longitudinal shaft between the individual printing units with an electrical longitudinal shaft. Thus, each printing unit receives a separate electrical drive. In addition to the high mechanical expense that continues to be necessary because of the complex nature of the individual printing units with a plurality of print positions, there is in this case a high expense for control technique, because synchronous operation of the individually driven printing units with one another must be guaranteed as well.
To avoid the above-mentioned problems, DE 41,38,479 A1 proposes that the cylinders of the printing machine be driven by one electric motor each.
DE 42,14,394 A1 discloses a process control system for such a printing machine with individually driven cylinders. The individual drives of the cylinders and their drive regulators can be arbitrarily integrated into print position groups. The print position groups are associated with folders, from which they obtain their position reference. The process control system proposed consists essentially of a high-speed BUS system for the individual drives and the drive regulators of a print position group and of a higher process control system for managing the print position groups.
Even though the design of the individually driven cylinders pursued in these two documents ensures a high level of flexibility in use, it also requires a very great number of drive motors at the same time, and, as is shown by DE 42,14,394 A1, a very high expense for regulating this great number of individual drives. Moreover, a great variety of motors must be used. If only a few motor sizes were used, it would otherwise frequently be necessary to use oversized motors for different applications. Both drive up the price of such a printing machine.
In contrast to the state of the art, the object of the present invention is to provide a rotary printing machine that can be used in a highly flexible manner and which is yet economical.
According to the present invention, blanket cylinders and plate cylinders of a rotary printing machine form in pairs a cylinder group, in which one blanket cylinder and one plate cylinder are mechanically coupled with one another and are driven together by a separate drive motor per cylinder group.
The number of the necessary drive motors is considerably reduced due to this group integration of the two cylinders and due to their being provided with a single drive for at least one cylinder pair; the number of the necessary drive motors is reduced by at least half compared with the individual drive designs. The mechanical coupling of these two cylinders, which are associated with one another in terms of printing technique, which is preferably a gear coupling with spur-toothed or helical gears, offers considerable advantages in terms of price over the design of the individually driven cylinders. No substantial concessions are to be made in terms of the flexibility of use compared with the individual drive design. Thus, both the circumferential register adjustment and the lateral register adjustment of each blanket cylinder can be performed individually and, if necessary, coordinated with each additional blanket cylinder. Technically and economically optimal print positions can be formed in a rotary printing machine due to the cylinder groups according to the present invention with separate drive motors. The print positions are defined in this connection as the cylinder pairs between which a web of paper to be printed on passes through and is printed on one side or on both sides. Consequently, one cylinder group and a corresponding counterpressure cylinder, which may, but does not have to, belong to the cylinder group, belong to a print position formed according to the present invention. However, the print positions of the printing machine are mechanically independent in terms of the drive technique in both cases, i.e., the print positions of the printing machine are electrically coupled with one another.
The blanket cylinder is preferably driven in the cylinder groups according to the present invention, and the blanket cylinder in turn drives the plate cylinder of the same cylinder group via the mechanical coupling. However, it is also possible to drive the plate cylinder shaft in another embodiment of the present invention, so that the blanket cylinder is driven only via the mechanical drive from the plate cylinder. While the drive of the plate cylinder advantageously requires a small effort for engaging and disengaging the blanket cylinder, the blanket cylinder is, on the other hand, decisive for the positional accuracy and the circumferential register adjustment. The first solution offers the advantage that the cylinder, which ultimately comes directly into contact with a web of paper to be printed on, does not need to be driven via a transmission member that may possibly have a clearance.
It is advantageous to always allow three cylinder groups to work on one print position. One cylinder group is arranged on one printed side, and two cylinder groups are arranged on the opposite printed side of a web of paper passing through between them. The blanket cylinder of the cylinder group arranged on one printed side of the web of paper preferably forms the counterpressure cylinder for the other two blanket cylinders of the cylinder groups arranged on the opposite printed side of the web of paper, and the latter cylinder groups are advantageously both driven alternatingly. This configuration offers the highest flexibility of use for a blanket/blanket production, because the two blanket cylinders that can be used alternatingly during ongoing production can be configured for changing over the print. This is performed by changing the plate of a plate cylinder associated with the non-engaged blanket cylinder. Each cylinder group can be mounted in an individual stand. The two cylinder groups located horizontally opposite one printed side of the web of paper are preferably integrated into a cylinder unit mounted in a stand.
According to the present invention, a cylinder group can be expanded by one counterpressure cylinder for the blanket cylinder. This third cylinder of the cylinder group thus formed is mechanically coupled with the blanket cylinder, preferably by an additional gear coupling. Such a cylinder group already represents a print position, between the blanket cylinder and counterpressure cylinder of which the web of paper to be printed on is passed through. The counterpressure cylinder may be a steel cylinder or another blanket cylinder for two-sided printing. Such a counterpressure cylinder may also especially be a central cylinder of a cylinder unit with, e.g., nine or ten cylinders. In an alternative, equally preferred embodiment of the present invention, such a central cylinder is driven by a separate drive motor. This type of integration guarantees the highest flexibility of use for a cylinder unit. Thus, each of the cylinder groups associated with the central cylinder can be reversed in this case individually and independently from the other cylinder groups, which is necessary, e.g., for alternate printing or for flying plate change.
The individual cylinder group is driven from a drive motor by means of a toothed belt. Such a toothed belt has a high elasticity compared with the solution proposed in DE 41,38,479 A1, according to which the rotor of the electric motor is mounted on the drive shaft of the driven cylinder. However, as will be explained later, the high damping of the mechanical system consisting of a drive motor and the driven cylinders is of great value for the control design of the drive of a cylinder group. However, the present invention also permits, in principle, direct drive, which may even be advantageous in the case of small cylinders. Compared with a gear drive between the drive motor and the driven cylinder of a cylinder group, which may also be used, a toothed belt offers the advantage of a clearance-free operation and of a not absolutely fixed transmission ratio.
In contrast, gears are provided for the mechanical coupling between the cylinders within one cylinder group, even though other transmission members are also conceivable. The mutually meshing gears may be spur gears or helical gears. In the case of spur gears, the blanket cylinder is longitudinally displaced for lateral register adjustment, while its driving and/or driven gears remain stationary according to the present invention. Otherwise, a circumferential register adjustment would also be necessary along with the lateral register adjustment. When spur gears are used, the blanket cylinder is simply displaced longitudinally together with its stationarily arranged gear or gears.
The inking roller or inking rollers of an inking system, which is/are associated with one cylinder group, can be mechanically coupled with that cylinder group according to the present invention, so that the inking roller or inking rollers is/are also driven from the drive motor of that cylinder group. The expense in terms of control (also referred to herein as control technique) can be kept low due to this solution. On the other hand, the mechanical coupling of the inking system according to the modular system pursued by the present invention is not quite so ideal as the more highly preferred individual drive for the roller or rollers of the inking system. Thus, each inking system has a separate drive motor for its inking rollers. Such a drive motor also preferably drives the inking roller or, in the case of a plurality of inking rollers, the inking roller located closest to the plate cylinder of the corresponding cylinder group via a clearance-free toothed belt with high damping and, if desired, via a reduction gear. The circumferential velocity of this inking roller is advantageously adjustable, especially with a negative slip in relation to the plate cylinder, so that the circumferential velocity of the inking roller is somewhat lower than that of the corresponding plate cylinder.
The positions of at least the drive motors of the cylinder groups of one cylinder unit operating on the same printed side of a web of paper are advantageously controlled. A so-called ideal position control, i.e., a delay-free position control with contouring error correction is preferred. However, this expensive type of position control, which is desirable for technical reasons, can be definitely dispensed with. A simple position control also represents a preferred, especially inexpensive embodiment of the present invention.
The position and/or the speed of rotation of the cylinder of a cylinder group or of a roller of an inking system to be controlled are controlled according to the present invention by means of a regulator for the drive motor by the variance comparison of the output signals of a set value transducer and of an actual value transducer, wherein the actual value transducer determines the position and/or the speed of rotation of the cylinder or roller. In contrast to the prior-art controls in rotary printing machines, a load transducer is thus used for control. In contrast, a mechanical transducer on the motor side has hitherto been used in the construction of printing machines to determine the motor speed or the angular position of the rotor of the motor for the variance comparison of the motor control. The dynamic limits are rapidly reached with this prior-art control in the case of high mass inertia ratios of the load to the motor. If the control becomes unstable, especially the motor begins to vibrate, while the load remains relatively still.
Difference correction means, control cascades, and active filters are used in control technique for so-called two-mass oscillators, but they require a high expense for control technique. It was surprisingly found to be fully sufficient for the above-described load/motor systems, i.e., the individually driven cylinder groups, to lead the control essentially by means of an actual value, which was determined by an actual value transducer arranged on the load, namely, on one of the cylinders of a cylinder group. This actual value-distance-angular position and/or speed of rotation of the corresponding cylinder is already sufficient alone to achieve high dynamics and control performance.
By obtaining the actual value to be controlled according to the present invention from the load, what must operate accurately, namely, the load, rather than the motor, is measured. The mechanical equivalent system consisting of the drive motor, a coupling and the load can be considered to be a low-pass filter. The low-pass filter of the motor-coupling-load-distance system is used in this type of control to filter impacts and vibrations, which are generated in the control system. Such impacts and vibrations are thus fed back into the regulator to a reduced extent. The risk of a build-up is reduced as a result. The dynamics of the control and consequently also the control performance can be substantially increased as a result compared with the prior-art control described, with identical coupling.
The actual value transducer, which has migrated, symbolically speaking, from the motor side to the load side, forms the principal controlled variable for the regulator of the motor, i.e., the motor is led from the load side by its actual value. According to an especially preferred embodiment of the present invention, no mechanical actual value transducer is needed for determining the position or the speed of rotation of the motor within the framework of the control of the motor. An actual value determination that may optionally be integrated within the motor can advantageously be used for exclusive drive monitoring, if desired, for switching off the motor.
The actual value transducer for the control is arranged, according to the present invention, at the torque-free shaft end of the driven cylinder of a cylinder group or of the driven roller of an inking system.
Asynchronous electric motors are used especially advantageously as the drive motors. An asynchronous motor has hitherto been used only when a small load was to be driven by means of a large motor. The use of asynchronous motors has been known for this case, in which a drive motor drives a cylinder group or even the rollers of an inking system, in which the mass inertia ratio of the load driven to the drive motor is relatively high. Asynchronous motors are particularly suitable for the purpose of control according to the present invention with a load transducer instead of a motor transducer. Asynchronous motors have a higher field rigidity than the d.c. motors used to date for these applications, so that their use improves the dynamics and the control performance of the system to be controlled. However, the use of other types of motors, e.g., d.c. motors, is not excluded, in principle.
The stability of the control is additionally improved by the preferred use of a clearance-free toothed belt with high damping as a coupling means between the motor and the load.
The drive motor may even be left out of consideration in the two-mass oscillator in question. The load, acting as a low-pass filter, is insensitive to the vibrations of the motor, which is much smaller compared with it. On the other hand, the reactions from the load to the drive motor can be ignored.
A maximum of flexibility is achieved with the design of integrating blanket cylinders and plate cylinders in pairs into cylinder groups, and, if desired, along with another counterpressure cylinder, while the price of a printing machine thus organized can be considerably reduced compared with a printing machine with individually driven cylinders. Drive motors of only two or at most three output classes are needed for a printing machine composed of such cylinder groups, while separate motors for cylinders with a great variety of different lengths and diameters are basically required in the case of directly and individually driven cylinders. The mass inertia ratios of the load to the motor, which may possibly vary within a wide range, can be absorbed and adjusted to one another by means of the toothed belt drive used according to the present invention. The reduction in the number of drive motors, together with the advantage that motors of only a few output classes must be provided, already offers considerable advantages in terms of price. This advantage is further enhanced by the use of the simple control according to the present invention, which is also flexibly adaptable to varying mass inertia ratios. The advantages achieved with the present invention become increasingly significant with increasing size of the printing machines, i.e., with increasing number of printing units and print positions per machine. The present invention is used especially in the construction of rotary offset printing machines, but it is not limited to them.
Preferred exemplary embodiments of the present invention will be explained below on the basis of the figures. Additional features and advantages of the present will be disclosed.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.